One‐Pot Organocatalytic Michael Addition/I2‐Mediated Cyclization Sequence: Metal‐Free Synthesis of Spiropyrazolones from 1,3‐Diketones and Unsaturated Pyrazolones
A highly efficient organocatalytic Michael addition/I2‐mediated cyclization reaction sequence between 1,3‐diketones and unsaturated pyrazolones was achieved in the presence of a chiral cinchonidine‐derived squaramide catalyst and I2 under mild reaction conditions. A variety of optically active spiro...
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Veröffentlicht in: | European journal of organic chemistry 2017-06, Vol.2017 (22), p.3152-3160 |
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Sprache: | eng |
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Zusammenfassung: | A highly efficient organocatalytic Michael addition/I2‐mediated cyclization reaction sequence between 1,3‐diketones and unsaturated pyrazolones was achieved in the presence of a chiral cinchonidine‐derived squaramide catalyst and I2 under mild reaction conditions. A variety of optically active spiro‐dihydrofuran pyrazolones were obtained in good to high yields (71–97 %) with excellent diastereoselectivities and high to excellent enantioselectivities (up to >99:1 dr and 99 % ee). A gram‐scale synthesis of chiral spiro‐dihydrofuran pyrazolones was also successfully realized.
A highly efficient organocatalytic Michael addition/I2‐mediated cyclization reaction sequence between 1,3‐diketones and unsaturated pyrazolones was achieved. A variety of optically active spiro‐dihydrofuran pyrazolones were obtained by using this method. The gram‐scale synthesis of chiral spiro‐dihydrofuran pyrazolones was also successfully realized. |
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ISSN: | 1434-193X 1099-0690 |
DOI: | 10.1002/ejoc.201700474 |